Aortic Diseases:

The aorta is a “hockey stick” shaped vessel that takes blood from the heart to all the body organs. It has several important branches that come off it. The first are the left and right coronary arteries that supply the heart muscle with blood. After that branches pass to the right arm and right neck (right carotid artery), followed by a branch to the left neck, then the left arm (left carotid artery). After that, the aorta tracks downwards, supplying branches to the spine, abdomen then the pelvis and legs. The main diseases affecting the aorta include aneurysm formation (stretching) and dissection (tearing). Any process that allows the aortic vessel wall to weaken will allow it to stretch and balloon out. Similarly, if the inner lining of the aorta becomes weakened, it can tear.

Aortic Aneurysm:
The two main areas that can stretch are thoracic aorta (thoracic aneurysm) and the abdominal aorta (abdominal aortic aneurysm). It is important to realise that for most patients, aneurysms are not symptomatic, and only revealed either by chance on routine X-ray and ultrasound scans. In the presence of risk factors that are known to damage the arterial wall such as hypertension, high cholesterol or smoking, it is always prudent to exclude the condition. 

Equally as one can be born with inherent weakness of the vessel wall and this can be genetic. A family history of aneurysm is important, so it may be useful to screen family members by imaging techniques. One important genetic condition is Marfans Syndrome, where there is inherent loss of elastic tissue affecting connective tissues that bind body parts together. The condition is often suspected in rather slender individuals who appear double jointed due to lax ligaments. In such patients it is worth excluding aortic problems as well as other cardiac manifestations such as leaky heart valves.This condition is genetic, and other family members should be screened.

Hypertension is the most common cause of aneurysm formation, where the high pressure exposes the weakness of the vessel. Other inherent problems resulting in aneurysm include patients with a double leaflet aortic valve (instead of the normal three leaflets). This is called “bicuspid aortic valve” disease and is associated with stretching of the early part of the aorta.

Clinical Symptoms of Aortic Aneurysm:  In most patients the condition is asymptomatic but may be suggested by a family history or the presence of risk factors. However in some patients an abdominal aneurysm may be suggested by the presence of abdominal pain, and associated with abnormal pulsation when the abdomen is examined. This is not always easy as in obese patients it may not be readily felt, and in thin patients, prominent pulsation may be normal. In thoracic aneurysm patients may present with chest pains or breathlessness. For any patient with sudden onset of sharp chest pain going through to the back, aortic dissection needs to be urgently excluded.

Clinical Investigations in Aortic Aneurysms: Routine chest X rays may sometimes suggest thoracic aortic enlargement. For more subtle stretching, an echocardiogram may determine and quantify it if it occurs in the early part of the aorta. Otherwise, transoesophageal echocardiography can better demonstrate stretching and dissection in most of the “hockey stick” section of the aorta. For abdominal aortic disease which is more common (5% of men > 65 years), conventional ultrasound is the mainstay of investigations. All the above techniques can help measure the degree of stretching. Serial measurements can be performed to monitor the progression of stretching. CT and MRI are perhaps the most thorough means of investigating the whole of the aorta. Indeed for abdominal aneurysms, CT is preferable.

Management of Aortic Aneurysms: Just because a patient has a stretched aorta, does not mean it necessarily needs fixing. The most important strategy involves controlling aggravating risk factors. The most important one is hypertension, where one would have a lower threshold of treating blood pressure. The only major lifestyle limitation is that of type of exercise. Isometric exercise, that is to say, straining exercises such as weight lifting, or straining against a fixed object should be discouraged. This is because of the small but significant risk of dissection. Isotonic exercise is recommended on the whole, but if it is of high intensity, exercise treadmill testing is recommended, to rule out large increases in blood pressure (> 180 mmHg). For most asymptomatic patients management involves serial scan measurements either six monthly or yearly to see if the vessel stretches further. This bears in mind that on average, aneurysms stretch by about 1 mm per year. For Marfans patients if the thoracic aorta stretches to beyond 5 cm, it needs fixing. For other patients, stretching beyond 5.5cm in the ascending aorta or beyond 6 cm in the descending aorta, the aorta needs fixing.

Abdominal aneurysms above 6 cm in diameter are associated with a significant risk of rupture. After serial monitoring, they tend to be repaired when they get to that stage. Family screening would be recommended as this is a genetic condition.

Treatment of Aneurysms: In the presence of significant symptoms or when the aorta has reached the recommended size then treatment is often necessary. For thoracic aneurysms, the operative mortality is low (3-5%), i.e. 95% success. Depending on whether the aortic valve needs replacing too, either a combined valve and root replacement patch graft, or just patch graft can be sewn in to replace the stretched vessel. Aneurysms of the arch of the aorta can be more complicated. For descending aortic aneurysm repair, the main concern is the slight increased risk of damaging the arterial branches to the spine. Fortunately, newer techniques have drastically reduced neurological complications for this area of surgery. More recently, instead of using a patch, a stent and patch can be used with further reduction in surgical risk of complications. For abdominal aneurysms, open repair of the aorta is the well tried and tested. The adverse prognostic risk is about 2%, but slightly higher in less fit patients. An alternative operation is a stenting procedure called an endovascular repair (EVAR). This obviates the need for open surgery, but not all patients are suitable for this technique.

Screening: As has been said, aneurysms on the whole are asymptomatic. Debates have raged as to the cost-benefit value of screening the general population. Some sort of consensus has been reached that for abdominal aneurysms, screening men and women between the ages of 60-85 with cardiac risk factors would benefit from assessment, or those aged 50+ with a family history of aneurysms. For thoracic aneurysms screening may be indicated in those with a family history, such as Marfans disease.